1. Technical Field
The present invention relates generally to leak detection and more specifically relates to a pipe joint leak detection apparatus which is used when a "test" or "tracer" gas pressurizes the pipe section adjacent the joint and leaks are tested by a detector sensing the presence of the test gas externally of the joint being tested in the event of a leak.
2. General Background
In the testing of oilfield drill pipe and the like, the joint between two adjacent sections of pipe must be tested before the pipe is put inot service. The integrity of the joint once it is assembled is tested by pressurizing the pipe bore adjacent the joint. The pipe bore can be "packed off" or sealed above and below the joint and the area between the seals then pressurized with a test fluid. One type of test involves the use of "helium" as a test or tracer gas. A "helium" test involves pressurizing the area around the joint and inside the pipe bore. A helium detector or "sniffer" then checks the area at the joint externally of the pressurized bore. The presence of helium as detected by the leak detector (a conventional, commercially available item) indicates a leak from the pipe bore through the threaded joint and into the atmosphere externally of the pipe bore. Helium is often used as a test or tracer gas because the helium molecule is very small and thus will pass through even the smallest unsealed area between the two threaded pipe sections, if in fact they are not assembled fully or properly.
U.S. Pat. No. 3,949,596 issued to Lawrence S. Hawk and entitiled "Leak Test Fixture and Method for Using Same" discusses as background information, the conventional prior art "helium leak test" and its use in the testing of pipe joints.
Other patents show various methods for testing leakage using helium.
U.S. Pat. No. 2,062,435 entitled "Method and Means of Detecting Refrigerant Leaks" provides a system which uses a member filled with a gas and rubber composition permanently spread or coated over the surface of the area to be tested and allowed to become set so that in the event of a leak of gas through the member the rubber will give a visible indication of the leak.
"Leak Detection" is the subject of U.S. Pat. No. 2,706,398 issued Apr. 19, 1955. That patent discusses a sampling probe having a body, an elongated tube affixed to and projecting from the body and having an orifice at one end remote from the body, a needle mounted in the body which extends through the tube and into the orifice, the body having a passageway connected between the tube and the exterior of the body, and conduit connecting the passageway with an analytical device.
A "Method and Apparatus for Testing and Protecting Gas Main Joints" is the subject of U.S. Pat. No. 2,766,614. The method uses a blanket which is wrapped around a joint adjacent the end portions of a gas main with the side edges of the blanket being drawn into tight sealing engagement with the gas main on each side of the joint. The tightened blanket remains on the joint a sufficient time for leaking gas to accumulate under the blanket and a hollow needle is connected to the blanket and to a gas indicating instrument through a self-closing hole in the blanket so as to sample the atmosphere within the blanket. Sampling this atmosphere determines whether or not gas is present in the atmosphere under the blanket and externally of the pipe joint.
U.S. Pat. No. 2,996,661 entitled "Leak Detector Proportioning Probe" shows a "Sniffing" probe for use in leak detection of vessels, pipes, and other closed systems.
A Method and Apparatus for the Detection of Leaking Gas is described in U.S. Pat. No. 2,550,498 issued to Chester Rice. Tracer gas is introduced into a closed system and its presence outside is detected as an indication of a leak by direct probing of the joints or fittings around the area suspect of leakage with an intake probe connected through the discharge device to a vacuum pump. The presence of a leak produces an increased amount of tracer gas in the region of the leak area which in turn produces a corresponding variation in current in the electrical discharge device circuit. Such variations may be indicated either through an instrument in circuit with the current or by a signaling device acutated at some preset amount of current.
U.S. Pat. No. 3,585,845 shows a "Gas Leak Detector" which uses a halogen-containing tracer gas which is introduced into a vessel to be tested for a leak. A probe is used through which air in the vicinity of a suspected leak may be drawn and diluted with an inert gas before being passed through an electron capture detector cell, the electric current through the cell serving to detect the presence of the tracer gas.
U.S. Pat. No. 3,592,048 issued to Louis P. Maurice et al. shows a "Portable Helium Leak Detector" wherein a first housing has an analyzer cell, the vacuum producing units and a vacuum connection arrangement to feed gas from the apparatus or arrangement that is being tested for leaks. If the helium gas to the unit being tested leaks and is fed to the analyzer cell, it will determine such to provide a signal. The second housing has the electronic portions, the indicating means and the control switches, such being connected to the first housing by an electrical cable connection. The second housing is separate from the first housing and is adapted to be placed close to the operators and remote from the first housing so as to be accessible to the operators so that they can read the indicators and can operate the control switches.
U.S. Pat. No. 3,690,151 relates to mass spectrometer leak detectors.
U.S. Pat. No. 3,762,212 provides a leak testing device forming a chamber wherein the device is placed in a test chamber following which a differential pressure is established between the chamber of the device and the test chamber. A tracer gas is introduced to the higher pressure chamber and communication is established between the lower pressure chamber and detecting apparatus such as a mass spectrometer which is sensitive to the tracer medium so as to detect any leakage of the tracer medium from the higher pressure chamber to the lower pressure chamber. At the inlet to the detecting apparatus is established a pressure chamber as to provide laminar flow from the lower pressure chamber to the inlet to the detecting apparatus.
U.S. Pat. No. 3,837,228 entitled "Tracer Gas-Permeable Probe for Leak Detectors" shows a leak detector system which employs a predetermined tracer gas, such as helium, the detector probe being provided with a plastic film which is selectively permeable to the tracer gas in preference to all other atmospheric gases.